1. Field of the Invention
The present invention relates to a magnetic toner used in development in image forming methods, such as electrophotography, electrostatic recording and toner jetting. The present invention also relates to an image forming method using the magnetic toner.
2. Description of the Related Art
Various developing methods have been used in practice in electrophotography. Among them, a one-component developing method using a magnetic toner is preferred because the method does not cause troubles and has a prolonged life and eased maintenance by the use of a developer with a simplified structure. In such a developing method, characteristics of the used toner significantly affect the quality of the image formation. The magnetic toner contains a magnetic material for imparting the magnetic property to the toner. Thus, the magnetic material affects the developing characteristics and durability of the magnetic toner. Various improvements have been proposed in terms of magnetic materials.
For example, a magnetic toner containing silicon and zinc is disclosed in Japanese Patent Laid-Open No. 8-101529. Magnetic materials containing silicon are disclosed in Japanese Patent Laid-Open Nos. 7-175262, 5-72801, 62-278131, 61-34070, 8-25747, 9-59024, and 9-59025. Magnetic materials containing silicon and aluminum are disclosed in Japanese Patent Laid-Open Nos. 7-110598 and 5-281778. Further, a magnetic toner containing magnesium is disclosed in Japanese Patent Laid-Open No. 5-345616. Although these magnetic materials have satisfactory developing characteristics, further improvement in their developing characteristics and durability is eagerly awaited, when they are used as a positively charged magnetic toner, when they are used in a high-speed developing machine, when a significantly large volume of copying is performed for a long period while repeatedly supplying the toner, when an amorphous silicon drum is used, or when a reversion developing is performed at a low potential in a digital machine.
Accordingly, it is an object of the present invention to provide a magnetic toner having excellent developing characteristics and durability.
It is another object of the present invention to provide a magnetic toner having excellent developing characteristics and durability on an amorphous silicon drum.
It is a further object of the present invention to provide a magnetic toner having excellent developing characteristics in low-potential development.
It is a still further object of the present invention to provide a magnetic toner having excellent developing characteristics and durability in a high-speed developing system.
It is another object of the present invention to provide a positively charged magnetic toner having excellent developing characteristics.
It is still another object of the present invention to provide an image forming method using the magnetic toner.
An object of the present invention is to provide a magnetic toner comprising a magnetic toner particle containing at least a binding resin and a magnetic material; wherein the magnetic material comprises a magnetic iron oxide containing 0.10% to 4.00% by weight of an element xcex1 from the third period to the seventh period with an atomic member from 11 to 103 in the long-period-type Periodic Table and having an electronegativity of 1.0 to 2.5, the solubility S1 of the element xcex1 in the magnetic material at an iron solubility of 0% to 20% lies in a range from 10% to less than 44%, the solubility S2 of the element xcex1 in the magnetic material at an iron solubility of 80% to 100% lies in a range from 5% to less than 30%, and the magnetic material contains (i) 60% by number or more of a type of multinuclear magnetic iron oxide particle, based on magnetic iron oxide particles, or (ii) 60% by number or more in total, based on magnetic iron oxide particles, of at least one type of magnetic iron oxide particle selected from the group consisting of polyhedral magnetic iron oxide particles having faces at ridgeline portions of hexahedron and polyhedral magnetic iron oxide particles having faces at ridgeline portions of octahedron, in combination with a type of multinuclear magnetic iron oxide particle.
Another object of the present invention is to provide an image forming method comprising a step of forming an electrostatic image on a latent image carrier and a step of developing the electrostatic image with a magnetic toner to form a magnetic toner image; wherein the magnetic toner comprises a magnetic toner particle containing at least a binding resin and a magnetic material; wherein the magnetic material comprises a magnetic iron oxide containing 0.10% to 4.00% by weight of an element xcex1 from the third period to the seventh period with an atomic member from 11 to 103 in the long-period-type Periodic Table and having an electronegativity of 1.0 to 2.5, the solubility S1 of the element xcex1 in the magnetic material at an iron solubility of 0% to 20% lies in a range from 10% to less than 44%, the solubility S2 of the element xcex1 in the magnetic material at an iron solubility of 80% to 100% lies in a range from 5% to less than 30%, and the magnetic material contains (i) 60% by number or more of a type of multinuclear magnetic iron oxide particle, based on magnetic iron oxide particles, or (ii) 60% by number or more in total, based on magnetic iron oxide particles, of at least one type of magnetic iron oxide particle selected from the group consisting of polyhedral magnetic iron oxide particles having faces at ridgeline portions of hexahedron and polyhedral magnetic iron oxide particles having faces at ridgeline portions of octahedron, in combination with a type of multinuclear magnetic iron oxide particle.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.